1. CENP-C Is a Structural Platform for Kinetochore Assembly
Marcin R. Przewloka, Zsolt Venkei, Victor M. Bolanos-Garcia, Janusz Debski, Michal Dadlez, David M. Glover 
Current Biology 
Volume 21, Issue 5, Pages (March 2011)
DOI: /j.cub
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2. Current Biology 2011 21, 399-405DOI: (10.1016/j.cub.2011.02.005)
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3. Figure 1
The Amino-Terminal Part of Drosophila CENP-C Does Not Localize to Centromeres but Binds the Entire KMN Network of Core Kinetochore Proteins
(A) Schematic representation of the N- and C-terminal parts of CENP-C used in this study.
(B) Localization of the EGFP-tagged C-terminal part of CENP-C (EGFP::CENPC-C) during interphase and mitosis. Cells were counterstained with anti-α-tubulin (MT), anti-CENP-A/CID antibodies, and DAPI (DNA). Scale bars in (B) and (C) represent 5 μm.
(C) Localization of the EGFP-tagged N-terminal part of CENP-C (EGFP::CENPC-N) during interphase and mitosis. Cells were counterstained as in (B).
(D) Proteins copurifying with the fusion protein A::CENPC-N with Mascot scores (Score) greater than 200. For CG numbers, refer to FlyBase entries ( The bait is indicated in red; KMN network components are indicated in blue. Spectral counts reflect the number of peptides identified for each protein. 1Note that coverage for the bait was scored as 35%. This figure refers to the full-length protein and corresponds to 63% coverage of the 788 amino acid fragment used as bait.
(E) Nnf1a binds CENPC-N in vitro, whereas MBP and Nsl1 do not. Upper panels show autoradiography of the indicated S35-labeled proteins. Coomassie-stained gels are shown in the lower panels to confirm equal loading of N- or C-terminal parts of CENP-C. Lanes are labeled as follows: M, marker proteins; In, input from the in vitro transcription-translation reaction not incubated with beads; N, in vitro-synthesized product incubated with GST::CENPC-N on beads; C, in vitro-synthesized product incubated with GST::CENPC-C on beads.
See also Figure S1.
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4. Figure 2
The CLD-Tagged N-Terminal Part of CENP-C Localizes to Centrosomes and Recruits KMN Network Kinetochore Components
(A) Schematic representation of the CLD construct, a fusion of EGFP with the centrosome-binding domain of SAK/Plk4, and the ect-KTR construct, a fusion of EGFP, the N-terminal part of CENP-C, and the same centrosome-binding domain. Both constructs localize to centrosomes when expressed in Dmel-2 cells.
(B) Cells expressing CLD or ect-KTR (EGFP, green) stained to reveal the dPlp centrosomal marker (red) and Mis12 (blue). DNA staining (at bottom, not merged) is shown only for ect-KTR.
(C) Cells expressing CLD or ect-KTR stained to reveal the centrosomal marker Spd2 (blue), the kinetochore proteins Nnf1a and Nnf1b (red), and the centromeric marker CENP-A/CID (green).
(D) Cells expressing CLD or ect-KTR stained to reveal the centrosomal marker Spd2 (blue), the kinetochore protein Spc105 (red), and the centromeric marker CENP-A/CID (green).
(E) Cells transfected with RFP-CLD (red) or RFP-ect-KTR (red) were cotransfected with EGFP::Ndc80 (green) and stained to reveal α-tubulin (MT; blue) and DNA (unmerged).
(F) Cells transfected with RFP-CLD (red) or RFP-ect-KTR (red) were cotransfected with CAL1::EGFP (green). CAL1::EGFP always colocalizes with CENP-A/CID (blue) on DNA (not merged) and does not colocalize with red signal of centrosomally targeted fusion proteins.
Scale bars represent 5 μm. Note that in this part of the study, we focused upon ect-KTR-expressing cells that did not show excessive scattering of chromosomes (see Figure 4 and associated text). This allowed us to ensure that any signal in the vicinity of the spindle poles was truly centrosome associated (and not centromere associated). See also Figure S2.
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5. Figure 3
Localization of CENP-meta and the Spindle Assembly Checkpoint Proteins Mad2 and BubR1 in CLD- and ect-KTR-Expressing Cells
(A) Cells expressing CLD (green) or ect-KTR (green) and stained to reveal CENP-A/CID (red) show localization of CENP-meta (blue) to ectopic sites in ect-KTR-expressing cells but not in CLD-expressing cells.
(B) Cells expressing CLD (green) or ect-KTR (green) and stained to reveal DNA (blue) and Mad2 (red) show localization of Mad2 to ectopic sites in ect-KTR-expressing cells but not in CLD-expressing cells.
(C) Cells expressing CLD or ect-KTR stained to reveal the kinetochore protein Spc105 (blue), the centromeric protein CENP-A/CID (green), and BubR1 (red). Staining of phosphohistone H3 is shown unmerged. Arrows indicate spindle poles in ect-KTR-expressing cells that have strong staining of Spc105 (blue) and weak staining of BubR1 (red). Stronger BubR1 staining is present on centromeres of such cells. Note that EGFP fluorescence from the CLD construct is much weaker than the signal from the fluorophore of the secondary antibody used for CENP-A/CID staining (the slide was bleached for some time to assure this effect). Arrowheads indicate such weak signals (“+ GFP” panel), which assure that the imaged cell is in fact transgenic.
Scale bars represent 5 μm.
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6. Figure 4
Sequestering of KMN Network Components to the Centrosomally Localized N-Terminal Part of CENP-C Leads to Chromosome Alignment Defects in Mitosis
(A) Cells expressing CLD ect-KTR or EGFP::CENPC-N (green), counterstained with anti-α-tubulin antibody (red) and anti-phosphohistone H3 (pH3) or DAPI to reveal DNA (blue). Scale bars represent 5 μm.
(B) Quantification of improperly congressed or scattered chromosomes in CLD-, ect-KTR-, and CENPC-N-expressing cells. 18% of the CLD-expressing cells (n = 130), 74.9% of the ect-KTR expressing cells (n = 177), and 75.6% of the CENPC-N-expressing cells (n = 41) showed chromosome positioning or spindle defects.
(C) Correlation of spindle length with chromosome congression and/or scattering defects in CLD, ect-KTR, and CENPC-N cells. Mean spindle lengths are CLD cells, 6.83 ± 0.78 μm (n = 25); ect-KTR cells, 8.7 ± 1.93 μm (n = 45); CENPC-N cells, 8.04 ± 1.27 μm (n = 41). The trend shows that longer spindles correlate with a higher frequency of chromosome congression defects.
(D) Depletion of Mis12 and Spc105 proteins from endogenous kinetochores. Kinetochore protein staining intensity values (background subtracted) were divided by the intensity values of CENP-A/CID staining at the corresponding centromere (background subtracted). Mean values for Mis12 are CLD, 0.92 ± 0.4 (n = 64); ect-KTR, 0.42 ± 0.34 (n = 78); CENPC-N, 0.25 ± 0.2 (n = 85). Mean values for Spc105 are CLD, 0.92 ± 0.33 (n = 61); ect-KTR, 0.27 ± 0.24 (n = 83); CENPC-N, 0.36 ± 0.27 (n = 114). See text for description and interpretation.
See also Figure S3.
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